Navegando por Orientadores "MOURA, Candido Augusto Veloso"

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Acesso aberto (Open Access)
Aplicação da composição isotópica de multielementos no monitoramento ambiental de área circunvizinha à barragem de rejeito: o caso da mina de cobre da Serra do Sossego, Canaã dos Carajás – PA
(Universidade Federal do Pará, 2017-06-09) OLIVEIRA, Simone Pereira de; MOURA, Candido Augusto Veloso; http://lattes.cnpq.br/1035254156384979
Tailings dams from ore mining activities are relevant compartment for environmental monitoring because the dam can present undesirable forms of water outlets such as infiltration. The present thesis proposed multielement isotope study in order to evaluate the use of the isotopic composition of oxygen, hydrogen, strontium and lead as a tool for the environmental monitoring of groundwater vulnerable to the tailings dam. This research was conducted in the area of the Serra of Sossego copper mine and, in addition to the isotope study, the hydrochemical characterization of groundwater and surface water was caried out. Besides, the direct reading of the isotopic composition of lead (without chemical treatment of the water sample) was applied for the first time, using multicollector inductively coupled plasma mass spectrometry, in the laboratory Para-Iso. The hydrochemical characterization of groundwater in the Serra do Sossego mine area showed that it is moderately acid (pH ~ 6). Only the AP15 and PS32 wells, under the influence of the drainage of the mixed pile (ore waste + sterile), presented high electrical conductivity (599 μS / cm2 and 694 μS / cm2) and the higher sulfate content (1.82 to 6.57 Meq/L). In general, iron (29.7 mg/L), manganese (69.7 mg/L) and copper (24.9 mg/L) present the highest metal content in the groundwter. In terms of the isotope studies, the groundwater of PS17, PS04, AP15 and PS32 wells and the water of the Dam present the least radiogenic lead isotopic composition. The water sampled in the AP15 and PS32 wells would be representative of the lead isotope signature of groundwater in the mine area (206Pb/207Pb = 1.1481 to 1.1663) and, probably, is indicative of the lead isotope composition of the meteroric water. The lead isotope composition of the groundwater of the wells PS04 (206Pb/207Pb = 1.1784-1.1850) and PS17 (206Pb/207Pb = 1.2100 to 1.2160) may indicate a small contribution of the rocks of the region (206Pb/207Pb > 1.6807). In turn, the lead isotope signature of water of the Dam (206Pb/207Pb = 1.2279) suggests, as expected, a slightly more pronounced contribution of the ore and the rocks. On the other hand, the lead isotopes of the water sampled in the wells MNA23 and PS06 show a more radiogenic signature (206Pb/207Pb = 1.6741 to 1.9196), which is similar to those of the chalcopyrite and the diabase of the Sequeirinho open pit, revealing a more significant contribution of the ore and rocks. As the lead isotope composition of water from the dam is different from that of the groundwater, it can be used for the environmental monitoring of the influence of the water from the dam in groundwater in the Serra of Sossego mine area. In those wells with less radiogenic lead isotope signature, a possible contribution of the water from the dam would result in a more radiogenic lead isotope composition in the groundwater. Conversely, in those wells with more radiogenic lead isotope signature, a contribution of the water dam for the groundwater would decrease the values of the measured lead isotope ratios. On the other hand, the application of the sulfur isotopes for environmental monitoring presented some limitation in the study area, due to the lack of contrast of the sulfur isotope composition among the sulfides of the Sossego deposit (δ 34S ~ 2-7 ‰), the water from the dam (δ 34S ~ 2 ‰), and the drainage of the mixed pile (δ 34S ~ 2‰). This prevents the recognition of a possible contribution of the tailings dam to groundwater. Mixing models using the 87Sr/86Sr ratio as a function of the strontium concentration and δ 18O values, also showed some limitations, since there is no contrast between the values of the 87Sr/86Sr ratio of the water from the dam (0. 7458 to 0.7539) and the rocks of the mine area (granite ~ 0.7474). Such similarity, in principle, would not allow identifying the contribution of the water from the dam. However, since groundwater generally exhibits less radiogenic values of the 87Sr/86Sr ratio (0.7161 to 0.7283) and well below the dam values, the strontium isotopic composition can be used for environmental monitoring of groundwater. Hydrogen and oxygen isotope data revealed that, in the rainy season, the groundwater presented values of δ 18O and δ D varying from -2.74 to -7.17‰ and from -15.6 to -46.0‰, respectively. In turn, an enrichment of 18O and D, with values of δ 18O between -1.67 and -7.29 ‰ and of δ D between -0.23 and -46.1 ‰, is observed in the dry season. Hydrogen and oxygen isotope composition of the water from the dam (δ 18O from 1.24 to 2.79 ‰ and δ D from 1.40 to 7.0 ‰) is very different from those of the groundwater and of the drainage of the pile. A mixing model performed with oxygen and hydrogen isotopes showed that these elements are the ones that best respond as indicators of the contribution of the waters from the dam to groundwater. The application of this model revealed no influence of the water from the dam on the groundwater during the period of this study. The results obtained in this multielement isotopic study suggest that the environmental monitoring of the groundwater of the Serra do Sossego mine to investigate the possible contribution of the water from the dam, can be done more efficiently with the oxygen and hydrogen isotopes. The isotopic compositions of lead and strontium can also be used for monitoring the groundwater, but this has to be done more systematically due to the small contrast between the isotopic composition of these elements in the dam water and in the groundwater. Finally, the isotopic composition of sulfur is the one that would contribute least to the environmental monitoring of the groundwater of the study area.
Acesso aberto (Open Access)
Datação pelo método de traços de fissão em apatita da região da estrutura dômica de Monte Alegre, Bacia do Amazonas (PA)
(Universidade Federal do Pará, 2011-04-05) NEGRÃO, Sílvia Cristina Barroso; LELARGE, Maria Lidia Vignol; MOURA, Candido Augusto Veloso; http://lattes.cnpq.br/1035254156384979
In the northern portion of the Amazonas Sedimentary Basin, south of the Monte Alegre city (PA), a semi-elliptical structure defined by a group of small hills occurs, which is known as the Monte Alegre Dome. In the central portion of the dome, Devonian rocks of the Ererê Formation crop out, while toward the edge of the structure the Neodevonian to Mesocarboniferous successions, represented by the Barreirinha, Curiri, Oriximiná, Faro and Monte Alegre formations, are exposed. Diabase dykes and sills of about 200 Ma (Penatecaua Magmatism) cut this set of rocks. The formation of this dome structure has been related to the emplacement of dykes and sills of diabase. However, the contribution of Tertiary tectonism, present throughout the Amazon Basin, cannot be ruled out for the formation of the dome, since in the eastern and southern portions of this structure the Cretaceous to Tertiary rocks of the Alter do Chão formation are in faulting contact with rocks of the Ererê formation. In this study we applied the apatite fission track thermochronology in the diabase of the Penatecaua Magmatism in order to determine the age of formation of the dome structure, and to investigate the role of the Tertiary tectonics in the development of this structure. The apatite fission track method (AFT) is applied to study the thermotectonic evolution of a region, since the quantification of the fission tracks present in the mineral permits to estimate the age at which the rock passed through a given temperature (blocking temperature), which may be related to a tectonic event (uplift / subsidence) that occurred in the area. The mafic rocks studied in the region of Monte Alegre provided ATF apparent average ages between 53.2 and 43.6 Ma. These ages are interpreted as representing major tectonic events that occurred in the Tertiary (Early to Middle Eocene) that uplifted to shallower crustal levels and the diabases and the country rocks. The thermal histories obtained after modeling the AFT data allowed the recognition of four events of cooling, which occurred at 140-110 Ma, 110-100 Ma, 55-45 Ma and 30 Ma-recent. Just one sample (TFMA-12), located outside of the dome structure, did not record the Eocene tectonic event. The ATF data modeling also permitted to estimate cooling rates ranging from 0.4ºC / Ma for slower events, up to 2.82°C / Ma for faster events. Based on these cooling rates it is suggested that 3 to 3.35 km of rocks section was removed due to the reactivation of faults at different moments during the geologic evolution of the region, mainly along the Cenozoic. The apparent ATF ages between 43.6 and 53.2 Ma, as well as the significant cooling thermal event recorded in the Eocene by the data modeling revealed the important role that the Tertiary (Eocene) tectonic in the formation of dome structure of Monte Alegre. It is believed that the apparent ages of fission tracks (43.6 and 53.2 Ma) would place limits on the age of this Tertiary tectonics.
Acesso aberto (Open Access)
Determinação da composição isotópica de chumbo e estrôncio em petróleo e derivados como ferramenta para o monitoramento ambiental
(Universidade Federal do Pará, 2010-04-13) LIMA, Cristiane Souza de; MOURA, Candido Augusto Veloso; http://lattes.cnpq.br/1035254156384979
O petróleo e seus derivados são vastamente utilizados nos dias atuais para as mais diversas atividades, entretanto, estas substâncias são também importantes fontes de poluição de compostos orgânicos nocivos aos seres vivos, e de introdução de metais pesados no meio ambiente. Dessa forma, o monitoramento de sedimentos, solos e águas naturais em áreas de processamento, armazenamento, manuseio e transporte de hidrocarbonetos deve ser constante para prevenir a contaminação ambiental decorrentes de pequenos vazamentos. Esse monitoramento é feito com a análise de substâncias orgânicas que são biodegradáveis. Alternativamente, ele pode ser realizado pela análise isotópica de metais presentes em pequenas quantidades nessas substâncias. Entretanto, a especificidade das técnicas analíticas envolvidas na extração de metais de substâncias orgânicas não incentiva o uso da composição isotópica de metais no monitoramento ambiental de hidrocarbonetos. Assim, neste trabalho aplicou-se procedimentos usuais na análise de materiais inorgânicos como rocha e solo na extração de metais em petróleo e derivados, com o objetivo de determinar a composição isotópica de chumbo e estrôncio nessas substâncias. As substâncias utilizadas nos procedimentos analíticos foram petróleo, gasolina, biodiesel, óleo lubrificante novo e óleo lubrificante usado. As duas últimas foram utilizadas para comparar eventuais mudanças na composição isotópica do chumbo e estrôncio após o seu uso em motores automotivos. Durante os procedimentos laboratoriais procurou-se encontrar as quantidades adequadas de cada tipo de amostra, para garantir a exatidão e precisão dos resultados analíticos. A implementação da metodologia de extração de metais de petróleo e derivados é o ponto central deste trabalho, onde procurou-se desenvolver um procedimento usando a infraestrutura laboratorial existente com segurança. Assim, o procedimento adotado envolveu a secura das amostras, seguida de calcinação para eliminação de matéria orgânica; dissolução da amostras com ácidos inorgânicos; separação cromatográfica do chumbo e estrôncio utilizando resina especifica de Sr (Sr.Spec); e determinação da composição isotópica de chumbo e estrôncio por espectrometria de massa. Após a realização de diversos ensaios verificou-se que as seguintes quantidades seriam adequadas para a análise isotópica de chumbo e estrôncio: petróleo (5 mL), gasolina (20 mL), biodiesel (20 mL), óleo lubrificante usado (5 mL), óleo lubrificante novo (30 mL). As composições isotópicas de chumbo e estrôncio variam dentro de um estreito limite para as substâncias estudadas. No caso do chumbo, com a razão 206Pb/207Pb apresentado os seguintes valores: petróleo (1,156), biodiesel (1,153), gasolina (1,136), óleo lubrificante novo (1,148) e o óleo lubrificante usado (1,138). Para o estrôncio a razão 87Sr/86Sr apresentou os seguintes valores: petróleo (0,70795), biodiesel (0,70896), gasolina (0,70769), óleo lubrificante novo (0,70812) e óleo lubrificante usado (0,70762). Os valores da razão 206Pb/207Pb do petróleo e derivados são semelhantes àqueles determinados na região metropolitana de Belém e atribuídos a fontes antropogências (~1,140) e, bastante distintos dos valores encontrados para fontes geogênicas (~1,192) nesta mesma região. Essas diferenças nos valores da razão 206Pb/207Pb tornam possível o uso da composição isotópica de chumbo para investigar eventual contribuição antropogênica em sedimentos e solos, proveniente do manuseio, armazenamento e transporte de petróleo e derivados. Por sua vez, a comparação da composição isotópica do estrôncio em petróleo e derivados com àquelas de água subterrâneas na região bragantina, no estado do Pará, por meio do parâmetro 87Sr(‰) mostra valores de 87Sr negativos para o petróleo e derivados, enquanto que para a água subterrânea eles são positivos. Considerando a significativa diferença apresentada nos valores de 87Sr acredita-se que a composição isotópica do estrôncio pode ser empregada como uma ferramenta alternativa para o monitoramento de águas subterrâneas em áreas onde ocorre ou ocorreu o processamento, armazenamento e o manuseio de petróleo e derivados.
Acesso aberto (Open Access)
Determinação da razão isotópica ⁸⁷Sr/⁸⁶Sr em águas naturais e sua aplicabilidade na investigação da influência da água do mar em águas subsuperficiais de zonas costeiras na Região Bragantina-PA
(Universidade Federal do Pará, 2000-08-25) SANTOS, Adriana Bordalo Braga; MOURA, Candido Augusto Veloso; http://lattes.cnpq.br/1035254156384979
Acesso aberto (Open Access)
Estudo da composição isotópica de Pb em organismo bentônicos, poliquetas (Namalycastis abiuma) e oligoquetas, da Baía do Guajará e rio Guamá
(Universidade Federal do Pará, 2009-06-24) OLIVEIRA, Simone Pereira de; ROSA FILHO, José Souto de; MOURA, Candido Augusto Veloso; http://lattes.cnpq.br/1035254156384979
In Guajará bay (Terminal Petroliferous do Miramar and mouth of Una Canal) and in Guamá river (mouth of Tucunduba creek), three samples of bottom sediments, three of polichaetes (Namalycastis abiuma) and five samples of oligochaetes (Tubificidae) were collected. In the biological samples lead (Pb) concentration and isotope composition were determined, whereas in the sediments samples only the Pb isotope composition was. Pb content was quantified in two representative samples of oligochaetes and polichaetes. Concentrations of 5 mg.kg-1 and 3 mg.kg-1, was obtained for these organisms, respectively. Pb concentration determined in oligochaetes was equivalent to 13% of the lead’s level of the bottom sediments of its habitat (38 mg kg-1). In spite of the Pb content of the bottom sediments of Guajará bay may suggest moderate pollution, this proportion can be considered high when it is compared with the percentual relation of 1,7% of oligochaetes and sediments of very polluted environments (p. ex. botton sediment lakes of India with lead content reaching 2.260 mg.kg-1 and oligochaetes with until 23 mg.kg-1). This result suggests that, proportionally, oligchaetes may assimilate greater amount of lead of its habitat in less polluted environments. However, the lead level in oligochaetes compared with the lead level in sediments of its habitat, showed a positive correlation, and it indicates that oligochaetes can be used as a bioindicator. The polychaetes (Namalycastis abiuma), did not show a trend that indicates any type of connection or correlation between lead level in organisms and lead level in sediments. This result indicates that polichaetes cannot be used as bioindicator of the enrichment of lead (and metals) in its habitat. Lead isotope composition of the bottom sediments in Guamá river, gave the value of 1,193 for the 206Pb/207Pb ratio which is different to the suggested a value of 1,194 for the bottom sediment of the Guamá river, and interpreted as the natural value (geogenic). This indicates a anthropogenic origin of lead in Guamá river in the sampled point (mouth of the Tucunduba creek). In Guajará bay, the sample of sediment in the mouth of the Una Canal, presented a value of 1,167 for the reason 206Pb/207Pb. In previous works, this value had been suggested as indicative of lead of anthropogenic origin. This value of 206Pb/207Pb ratio shows that the Una canal is contributing to lead level in the sediments of the Guajará bay, through of discharge of domestic effluent and solid residues. Finally, in a sediment sample collected in the Terminal Petroliferous do Miramar, also in the Guajará bay, the value of the 206Pb/207Pb ratio was 1,188. This value is lower than that suggested as natural value of the 206Pb/207Pb ratio in the bottom sediments of the Metropolitan Region of Belém, which is of 1,200. This lower value can be related to activities of the Terminal Petroliferous do Miramar. The products originated in oil have an important potential of heavy metal (including lead) dissemination to environment. In order to compare the lead isotope signature of the organisms with that of the sediments the values of the isotopic ratio 206Pb/207Pb of the organisms were divided by the respective values of thIs ratio in the sediments. If the resultant quotient, represented as R, had a value of 1± 0,004 (0,996 ≤ R ≤ 1,004), it was considered as indicative that the lead isotope signature of the organisms reflected the signature of the bottom sediments of its habitat. The values of R in 75% of the biological samples were within the interval (0,997 ≤ R ≤ 1,001). The other 25% that remain outside of this tolerance interval, correspond to the two samples of oligoquetas collected in the mouth of Una Canal. Thus, the three samples of polichaetes collected next to the Terminal Petroliferous do Miramar, and the three samples of oligoquetas collected in the Guamá river next to the mouth of Tucunduba creek show values of R within the tolerance interval. This suggest that the polichaetes (Namalycastis abiuma) and oligochaetes reflected the lead signature isotope of the environment in which they are inserted, and are good bioindicators of lead isotope composition in its habitat.
Acesso aberto (Open Access)
Estudo da razão isotópica 87 Sr /86 em macrofosséis da Formação Pirabas, nordeste do estado do Pará
(Universidade Federal do Pará, 2001-10-10) BELÚCIO, Elcinice Ferreira; MOURA, Candido Augusto Veloso; http://lattes.cnpq.br/1035254156384979
Acesso aberto (Open Access)
Estudo de Proveniência das rochas metassedimentares do Complexo Ceará, na região de Sobral e adjacências, com base em datação U-Pb de zircão e idades-modelo Sm-Nd
(Universidade Federal do Pará, 2015-06-05) FEITOSA, Jeremias Vitório Pinto; MOURA, Candido Augusto Veloso; http://lattes.cnpq.br/1035254156384979
The Borborema Province is an important tectonic province, with approximately 450,000 square kilometers in the northeastern Brazil, which registered numerous and remarkable geological processes that occurred on Earth over time. This province has great similarities with existing provinces in Africa, as the Benin/Nigeria. Successive geological cycles are recorded in rock types of the Borborema Province, dating back to a very complex geologic evolution started in the Archean, culminating at the end of the Neoproterozoic, with the occurrence of tectonic-thermal events and magmatism called the Brazilian Cycle, which resulted in the closure of an oceanic domain in this region. The Tamboril-Santa Quitéria Complex (TSQC) is the most significant unit of this final process of continental collision observed in Ceará Central Domain of the Borborema Province. The existent geochronological and isotopic data allow to understand the context and the geological evolution of the unit. However, for the metasedimentary rocks that flank the TSQC, assembled in the Ceará Complex, are lacking studies and information that permits to propose more refined geological models to better understand the evolutionary framework of this region. The suggested Paleoproterozoic age initially suggested for the metasedimentary rocks of Ceará Complex can questioned due to the presently known geological context. Thus, the sedimentary provenance study proposed here using U-Pb detrital zircon dating and Sm-Nd model-age (TDM), aims to investigate the maximum age of deposition of this metasedimentary unit, and the probable the crustal source of these rocks, to contribute to the understanding of the evolution and stratigraphic framework of Ceará Central Domain. This work included the sampling of 20 outcrops of these metasedimentary rocks that occur in the western and in the eastern flanks of the TSQC. Six samples of quartzite were collected for U-Pb zircon analysis using a laser ablation system attached to a multicollector mass spectrometer with inductively coupled plasma (LA-MC-ICPMS). Sm-Nd model-age determination was carried out in 14 samples. Petrographic study of the non-friable samples preceded the isotope analyses. The rocks of the western flanks of the TSQC were garnet gneiss and kyanite gneiss, with dominantly lepidoblastic and even granoblastic textures. Besides, sillimanite quartzite and muscovite quartzite occurs presenting polygonal granoblastic textures. In the eastern portion, the rocks were observed garnet gneiss with lepidoblastic and granoblastics textures in addition to garnet amphibolite with mainly nematoblastic and minor porphyroblastic textures. The Sm-Nd model-ages between 2.12 and 2.7 Ga., and positive values of Nd (2,1Ga) (+3.30 to + 2.60 ) suggests a strong contribution to Paleoproterozoic crust for the sediments located east of TSQC. This contribution is also recorded in the rocks sampled in the west of TSQC. However, TDM model-age of 1.66 Ga found in a rock also suggests contribution of younger crustal source for these metasedimentary rocks. The U-Pb data for quartzites of the Ceará Complex, in general, have prevalence of detrital zircons of Paleoproterozoic ages, more frequently of the Orosirian (1800-2050) and Rhyacian (2050-2300 Ma) periods, suggesting that the main source area of the sediments are Paleoproterozoic age. However the presence of detrital zircon grains of Statherian (1750± 50 , 1777± 58, 1628± 53 Ma) and Stenian age (1154 ± 29 Ma) found in rocks located east of TSQC indicates the input of younger rocks, corroborating the contribution of younger crustal source for the sedimentary succession of Ceará Complex. The age of 1154 Ma, indicates the maximum age of deposition of these sediments suggesting that this depositional event may even have occurred in the Neoproterozoic, as it is suggested by geological and geochronological evidences pointed out by some authors who studied this succession in other regions of Ceará Central Domain.
Acesso aberto (Open Access)
Evolução do embasamento Arqueano e Paleoproterozoico do Cinturão Araguaia com base em dados isotópicos U-Pb e Lu-Hf em zircão por LAMC-ICPMS.
(Universidade Federal do Pará, 2019-09-10) ASSIS, Clauber Roberto da Fonseca; MOURA, Candido Augusto Veloso; http://lattes.cnpq.br/1035254156384979
The basement rocks of the Araguaia Belt (AB) consists predominantly of Archean and Paleoproterozoic rocks. The former predominates in the northern segment while the Paleoproterozoic rocks prevail in the southern portion. To the north, the basement rocks crop out in the core of dome-like structures, and are represented mainly by TTG affinity Archean orthognaisses (Colmeia Complex), with minor Paleoproterozoic granitic gneisses (Cantão Gneiss). To the south the ortho- and paragnaisses of the Rio dos Mangues Complex (RMC) and the Serrote Granite (GS) are the main Paleoproterozoic rock units. Neoarchean (Rio do Coco Group) and Mesoproterozoic (Monte Santo Suite) rock units occur locally. Single zircon Pb-evaporation dating defined ages around 2.86 Ga for the Colmeia Complex (CC) orthognaisses. For CRM gneisses these ages were in the range of 2.05-2.08 Ga. In turn, the age of 1.86 Ga was obtained for GS that intrudes the CRM gneisses. Recent U-Pb zircon dating by LA-MC-ICPMS revealed different ages for the orthognaisses of Lontra (2905 ± 5,1 Ma) and Cocalandia (2869 ± 11 Ma) dome-like structures. Aware of the analytical limitations of the Pb-evaporation technique, this study resumed the dating of the CA basement rocks using the U-Pb zircon method by LA-MC-ICPMS. This investigation was complemented by the use of the Lu-Hf zircon system to understand the evolution of this crustal segment. The ages 2930 ± 15 Ma, 2898 ± 11 Ma and 2882 ± 9 Ma were determined for the orthognaisses of the Xambioá, Grota Rica and Colméia dome-like structures, respectively. These ages, together with those published for the orthognaisses of Lontra and Cocalândia dome-like structures, indicate that the igneous protoliths of the orthognaisses of CC were generated by distinct magmatic events spanning 60 Ma. The Hf-TDMC ages of the zircon crystals of these rocks indicate an origin from a juvenile crust formed in the Mesoarchean, with the largest contribution of older crustal material to the Grota Rica and Colmeia gneiss protoliths. An age of 2059.7 ± 6.4 Ma was obtained for an orthogneiss from the RMC. For a porphyritic metasyenogranite (GS) the age of 1868 ± 16 Ma was defined. Both ages corroborate the previously published Pb-evaporation ages. In both rocks, the Hf-TDMC ages and ƐHf (t) values occur at very similar intervals, indicating that they were generated from the same neomesoarchean source. Alternatively, the RMC orthognaisses could result from mixing between mesoarchean rocks and Paleoproterozoic juvenile crust. In this case, the GS could result from partial melt of the RMC gneisses. Two gneisses sampled as belonging to the RMC showed Neoproterozoic ages. The first one is a tonalitic orthogneiss whose protolith crystallized at 599 ± 15 Ma. It has inherited zircons ranging in age from 677 to 2990 Ma. The Hf-TDMC model ages of the crystals that defined the age of 599 Ma were between 1.43 and 1.97 Ga, with ƐHf (599 Ma) ranging from -10.90 to -0.88. These values suggest that reworking older crustal rocks, possibly with smaller contributions of Neoproterozoic mantle material, generated the tonalitic magma. The other rock is a sillimanite-rich paragneiss with detrital zircon ages between 594 and 2336 Ma.Therefore, the maximum age of the sedimentary protholite is less than 590 Ma. The Hf-TDM C model age values for these crystals indicate that the source rocks were generated predominantly by reworking older material. The metamorphic event that formed these younger gneisses is probably associated with the collision of the Goiás Magmatic Arc with the southern segment of the CA basement, within the context of formation of the Gondwana Supercontinent in the Neoproterozoic.
Acesso aberto (Open Access)
Evolução geológica pré-cambriana e aspectos da metalogênese do ouro do cráton São Luís e do Cinturão Gurupi, NE-Pará/ NW-Maranhão, Brasil
(Universidade Federal do Pará, 2004-07-06) KLEIN, Evandro Luiz; GIRET, André; HARRIS, Christopher; MOURA, Candido Augusto Veloso; http://lattes.cnpq.br/1035254156384979
In the Gurupi region, located at the border between the Pará and Maranhão states in northern Brazil, igneous and metamorphic rocks crop out as part of the Parnaíba Structural Province. Early geochronological studies, based on the Rb-Sr and K-Ar methods have shown two geochronological domains. The rocks that crop out towards the Atlantic margin showed a Paleoproterozoic signature, around 2000 Ma, whereas the rocks that crop out towards the inner portions of the continent showed a Neoproterozoic signature, especially between 800 and 500 Ma. These domains have been then defined as the São Luís Craton and Gurupi Belt, respectively. Several lithostratigraphic propositions have been developed throughout more than two decades. However, these propositions always lack robust geochronological support. Geotectonic models discussed a one- or two-phase evolution for the Gurupi Belt, also lacking robust geochronological and isotopic data to consubstantiate the interpretations. Furthermore, among the several gold deposits that occur in both the cratonic and belt areas, only a few have geological and genetic information. These subjects are addressed in more or less depth by this thesis. New propositions for the regional lithostratigraphy and geological evolution have been achieved in this work by revaluating the available geological, geochemical, geochronological and isotopic dataset, as well as by adding new geochronological data on zircon (Pb-evaporation, U-Pb ID-TIMS, and LAM-ICP-MS) for most of the igneous and orthometamorphic rocks in the region. Whole rock Nd isotope data have also been obtained, allowing the discussion of crustal accretion and reworking. The results show a rather complex geological evolution with intensive and extensive crustal growth between 2.24-2.15 Ga and crustal reworking, involving melting, migmatization, metamorphism, and deformation around 2.10 Ga. The following results have been obtained for the São Luís Craton: Aurizona Group, metavolcano-sedimentary sequence, maximum age of 2241 Ma (juvenile) that possibly evolved until c.a. 2200 Ma; Tromaí Intrusive Suite, calc-alkaline, metaluminous tonalites of oceanic island arc, 2168 Ma (juvenile); Areal Granite, calc-alkaline, weakly peraluminous, 2150 Ma (mixing of juvenile and arc materials). In the Gurupi Belt, the following results have been obtained: Igarapé Grande Metatonalite, small and localized granoblastic tonalite, 2594 Ma; Itapeva Complex, weakly migmatized tonalitic orthogneiss, 2167 Ma (mostly juvenile); Chega Tudo Formation, metavolcano-sedimentary sequence (back-arc basin?), 2150-2160 Ma; Maria Suprema Granite, syntectonic, peraluminous muscovite-bearing granite, 2100 Ma (similar to other peraluminous granitoids in the Gurupi Belt). The Gurupi Group is tentatively placed in the Paleoproterozoic (>2160 Ma), but this must still be proved. The above data are interpreted on a plate tectonics basis, as follows. An oceanic basin is open at ca. 2260 Ma and is followed by the onset of subduction, formation of island arcs and voluminous calc-alkaline magmatism in oceanic settings, and concomitant reworking of the arcs between 2170-2150 Ma. This set of oceanic terranes has been accreted (soft-collision) onto an Archean continental margin to southwest (Archean part of the Amazonian Craton or a present day concealed cratonic nuclei). The collision provoked the metamorphism, deformation, and partial melting of the newly formed Paleoproterozoic crust and of part of the Archean bloc, or their erosive detritus, migmatization, and emplacement of peraluminous granitoids at 2100-2080 Ma. The region has been the locus of a second event in the Neoproterozoic. A continental rift developed in the bloc that was assembled in the Paleoproterozoic, as attested by the intrusion of a nepheline syenite (Boca Nova) at 732 Ma. Sedimentary rocks that filled this rift (Marajupema Formation) have detrital zircon crystals that show the youngest ages around 1100 Ma. The rift evolved probably to an oceanic basin, as suggested by the widespread occurrence of detrital zircons with ages around 550 Ma in small sedimentary basins that have been filled with immature sediments. The precise time of orogenesis climax that followed basin closure, with mass transport from SSW to NNE and accompanying metamorphism, is not yet constrained. Equivocal geochronological information point to 650-520 Ma (zircon of the nepheline syenite, Rb-Sr and KAr ages in minerals). The metallogeny of selected gold deposits occurring in both the São Luís Craton and the Gurupi Belt is addressed using varied information, such as geology, chlorite chemistry, fluid inclusion geochemistry, and stable (O, H, C, S) and radiogenic (Pb) isotopes. Structural and textural relationships, and Pb isotope data indicate a post metamorphic peak and late- to posttectonic timing for the gold mineralization with respect to the Paleoproterozoic events (post 2080 Ma). At a regional scale, the deposits show a similar signature characterized by formation temperatures between 280° and 380°C; pressures of 2-3 kbars; low-salinity (5 mass % NaCl equiv), reduced and moderately dense aqueous-carbonic (CO2 <20 mol%, traces of CH4 and N2), showing strong evidence for phase separation. Stable isotope studies suggest distinct sources for fluids and solutes. The carbonate, graphite, and fluid inclusion carbon comes from two sources: a depleted organic source, and an unknown source that may be magmatic, metamorphic or mantlederived (or both). Sulfide sulfur derived directly from magmas or from the dissolution of magmatic sulfides. Combined oxygen and hydrogen isotopes attest a metamorphic source for the fluids. Therefore, dehydration and decarbonization reactions during the metamorphism of the Paleoproterozoic metavolcano-sedimentary sequences appear to have produced the mineralizing fluids. Gold was transported as a reduced sulfur complex, such as the Au(HS)2 - and precipitated in response to the breakdown of this complex due to phase separation and fluid-rock interactions. The geological and genetic constraints are consistent with the orogenic gold model, found in metamorphic belts of all ages. As a whole the results of this study have implications for the understanding of the Paleoproterozoic and Neoproterozoic orogenies that built up the South American Platform and for the assembly and break-up of the Atlantica, Rodinia, and West-Gondwana supercontinents. The geological scenario outlined here for the Paleoproterozoic shows good correlations with those found especially in the southeastern Guyana Shield and in the southern portion of the West- African Craton. For the Neoproterozoic, the available information is still insufficient to draw major correlations.
Acesso aberto (Open Access)
Geocronologia U-Pb e geologia isotópica Sm-Nd do Granito Rio Verde, Neoproterozoico no Terreno Granjeiro -Várzea Alegre (CE)
(Universidade Federal do Pará, 2019-12-20) COELHO, Dayane do Nascimento; MOURA, Candido Augusto Veloso; http://lattes.cnpq.br/1035254156384979
Several magmatic events, from the late Archean to the beginning of the Phanerozoic, are recognized in Borborema Province. The plutonic Ediacaran-Cambrian activity (Brasiliano cycle) is one of the most important geological features of this Province since it generated a large number of granitic bodies of different ages and nature. In this context, there are several granitoids emplaced in the Neoarchean rocks of the Granjeiro Terrain, of the Rio Grande do Norte Domain. Undergraduate geology students of the UFPA mapped some granitic bodies hitherto not described in this terrain yet. Among the new occurrences, a small granitic pluton located southwest of the city of Várzea Alegre-CE is the object of geochronological investigation of this dissertation. It is being referred here as Rio Verde Granite. The pluton presents porphyritic texture with feldspar phenocrysts (1,0 to 5,0 cm in size) immersed in a medium-grained matrix. The Rio Verde Granite has three lithofacies. Titanite-biotite-hornblende granodiorite (TnBtHbGdr), biotite monzogranite (BtMzg), and enclaves of quartz diorite composition. It also shows evidence of magmas mingling. The rocks are deformed; however, magmatic structures are also observed. The U-Pb zircon dating of the BtMzg and associated intermediate enclaves by LA-MC-ICP-MS was carried out to correlate this magmatism with one of the magmatic events recognized in the Borborema Province. In parallel, the Sm-Nd isotopic systematics was performed to characterize the source of the granitic magma (crustal rework or juvenile crust). U-Pb zircon dating provided a concordant age of 592 ± 3.2 Ma (2σ, n = 5) for the BtMzg. In turn, zircon dating in two samples of the quartz diorite enclave was not good enough due to the degree of metamictization of zircon crystals, which resulted in poor preservation of primary igneous features. Nevertheless, it was possible to define, in one of the samples, the concordant age of 607 ± 4.8 Ma (2σ, n = 3), which is indicative of the timing of the intermediate rocks. Thus, the contemporaneity between the granitic and the more mafic magmatism is suggested. However, additional geochronological studies are needed to define the age of the mafic magmatism accurately. The use of the Sm-Nd isotopic system in whole-rock revealed negative εNd (590Ma) values of -18.26 and -19.42, indicating the reworking old crust as source of the granitic magma. The Nd-TDM ages, calculated in two-stage, of 2.48 and 2.56 Ga, show the contribution of the Archean crust, probably of the Granjeiro Complex, to the formation of the magma that originated the Rio Verde Granite. However, the mixing of Archean crust with younger crustal material cannot be discarded as the Nd-TDM ages are in the Archean-Paleoproterozoic boundary. Considering the petrographic and geochronological features the Rio Verde Granite, it may be associated with the 570-590Ma syn-transcurrent granitic magmatism that occurred in the Borborema Province. This magmatic event has the granitoids of the Itaporanga Intrusive Suit as one of its representatives.
Acesso aberto (Open Access)
Geocronologia U-Pb e tipologia de zircão detrítico aplicadas a estudos de proveniência sedimentar das formações Piriá e Igarapé de areia, Cráton São Luís/Cinturão Gurupi (NE-Pará/NW-Maranhão)
(Universidade Federal do Pará, 2018-09-08) AMARAL, Rômulo Pinto; MOURA, Candido Augusto Veloso; http://lattes.cnpq.br/1035254156384979
Modern analytical equipment such as the Multicollector-Inductively Coupled Plasma Mass Spectrometer, connected to a Laser Ablation microprobe (LA-MC-ICP-MS), made U-Pb geochronological analysis of zircon more accessible and allowed the collection of large amount of data. As a result, the dating of detrital zircon grains has become an important tool in sedimentary provenance studies, since it may provide direct information about the ages of the igneous and/or metamorphic rocks of the source areas that contributed to the deposits of a sedimentary basin. This tool, together with the morphological analyzes of the dated detrital zircons, was applied to provenance studies on the sedimentary rocks of the Igarapé de Areia and Piriá formations, that crop out in the northeast of Pará and northwest of Maranhão states. These sedimentary successions occur in the midst of rocks of the São Luís Craton (SLC), and Gurupi Belt (GB) geotectonic domains. The former is of Paleoproterozoic age and the GSB incorporates significant portions of the SLC strongly reworked in the Neoproterozoic. The Igarapé de Areia Formation is composed of medium grain arcosian sandstones with trough cross stratification, marked by levels of opaque minerals, indicating deposition in medium to highenergy fluvial systems. The maximum depositional age of this unit is 1940 ± 55 Ma, and the sedimentary contribution is restricted to sources from the Rhyacian period (2052 - 2269 Ma), which is consistent with the age of crustal growth of Saouth American Plataform. The Piriá Formation occurs in both geotectonic domains. For the succession that lies over the GB, here called the West Segment, detrital zircons from two sandstones of the arkose and greywacke interbedded with pelitic layers lithofacies, and from one conglomerate of the conglomeratic lithofacies were analyzed. The geochronological dates from the sandstones present subordinate peaks of Neoproterozoic (509 - 951 Ma) and Mesoproterozoic ages (1243 - 1630 Ma), and a main peak of Paleoproterozoic age, mostly Rhyacian (2050 - 2266 Ma). The conglomerate facies is made up of ortho- and paraconglomerates whose constituents indicate igneous and metamorphic sources. The ages of the detrital zircon grains are basically between 1950 and 2298 Ma, which suggest, from the geochronological point of view, that the sediments may have come from a Paleoproterozoic source area, unlike the sandstones of this segment. On the other hand, the Piriá Formation rocks that occur on the SLCF, East Segment, correspond to arkose with plane-parallel stratification interlayered with siltites, and were probably deposited in portions of lower energy of fluvial channels. The histogram of cumulative ages of the detrital zircon from an arkose shows the predominance of younger source areas (525 - 824 Ma). The maximum depositional age for the Piriá Formation is estimated at 509 ± 17 Ma. The discrepancy in the distribution of zircon ages between the arkoses of the East and West segments of the Piriá Formation indicates the contribution of different source areas, suggesting that these segments could represent sub-basins or sedimentary successions deposited in different periods of time.
Acesso aberto (Open Access)
Geocronologia U-Pb em zircão detrítico aplicada ao estudo de proveniência dos arenitos do Grupo Canindé, borda leste da bacia do Parnaíba
(Universidade Federal do Pará, 2015-10-13) OLIVEIRA, Camila Vilar de; MOURA, Candido Augusto Veloso; http://lattes.cnpq.br/1035254156384979
The U-Pb dating by LA-ICP-MS of detrital zircons from Canindé Group allowed the establishment of a direct link between the ages of zircon grains from sandstones of the eastern edge of the Parnaiba sedimentary basin and the rock units in distal and/or proximal source areas, and showed that this technique is an indispensable tool for sedimentary provenance investigation. The studied siliciclastic succession are composed of diamictic, intraformational breccias, fine to coarse sandstones and, fine to very fine sandstones which are interdigitated with pelites and mudstones. This sedimentary sequence is represented by seven facies associations: a) the basal unit corresponds to lower offshore-shoreface deposits (Af1) of Pimenteiras Formation; b) gradually westward, crop out rocks of Cabeças Formation represented by subglacial deposits (Af2) intercalated with, and in erosive character, distal deltaic front deposits (Af3) - these deposits exhibit more proximal features in the northern, highlighted by sigmoidal lobes (Af4); c) the Longá Formation exposure is narrower, featuring deposits of distal deltaic front (Af5); d) the top unit, represented by the Poti Formation, shows deposits with offshore-shoreface marine features (Af6) in the northwestern portion, and more continental, with channel bar deposits (Af7), in the southwestern. The imaging of internal structure of 318 zircon grains of these sedimentary successions, by Scanning Electron Microscope with Cathode- Luminescence (SEM-CL), revealed four major populations: a) grains with concentric zoning (Zr1); b) homogeneous grains (Zr2); c) grains with convoluted zoning or recrystallized rims (ZR3); d) metamític or fractured grains with exsolved rims (ZR4). The density distribution diagrams (relative and cumulative probability) of the U-Pb ages, and the percentages of these ages in pie charts, show clear heterogeneous distribution of the zircon age spectrum. Paleoproterozoic zircon population (mainly Orosirian) predominates over Mesoarchean and Mesoproterozoic ones. In addition, important contribution of Neoproterozoic (largely Tonian) and Cambrian zircon populations shows up in most of the samples. The K-S test suggests strong similarity between the sources of Cabeças and Longá formations (p = 0.385) and, a clear difference of the provenance patterns between the Pimenteiras and Poti formations (p = 0). Paleocurrent measurements of the fluvial sandstones and of the unimodal deltaic sigmoids have shown that, during the deposition of Canindé Group, the source areas were located to the south and southeast of the current border of the Parnaíba basin. These areas include the west sector of the Borborema Province (BP) and the São Francisco Craton (SFC) with its surrounding Braziliano belts (Brasília and Rio Preto). Thus, it is suggested that the sediments of the eastern portion of the Parnaíba Basin, derived from the northern segment of the SFC (Sobradinho block) and the Central and South subprovinces of the BP. For the latter, the probable candidates would be the Alto Pajeú tarrain (Cariris Velho – sensu stricto) and the Riacho do Pontal belt. The sediment supply was fully controlled by marine incursions (transgressions and regressions) recorded from the Mesodevonian to the Eocarboniferous.
Acesso aberto (Open Access)
Geologia e geocronologia da região a sul de Paraíso do Tocantins-TO
(Universidade Federal do Pará, 1996-04-22) SOUZA, Silvia Helena Pereira de; MOURA, Candido Augusto Veloso; http://lattes.cnpq.br/1035254156384979
The most recent geochronological studies carried out in the basement of the northern segment of the Araguaia Belt indicated the occurrence of rocks from both the Archean and the Lower Proterozoic. The oldest rocks, predominantly represented by trondhjemitic orthogneisses, with ages around 2.85 Ga, were grouped in the Colméia Complex. On the other hand, granitic orthogneisses, with a minimum age of 1.85 Ga, called Cantão Gneisse, constitute the youngest rocks, hitherto known, from the basement of the Araguaia Belt. In its southern segment, the basement of the Araguaia Belt is represented by tonalitic gneisses, associated with calciosilicate gneisses, which were correlated to the Colméia Complex, and which serve as host for the Serrote Granite, located south of the city of Paraíso do Tocantins. Calciosilicate gneisses, quartzites and tonalitic gneisses were also described, gathered in a distinct unit called Complexo Rio dos Mangues. Although the units mentioned above were considered Archean in age, there is practically no geochronological information about them. This work, therefore, aims to determine the ages of the basement rocks in the southern portion of the Araguaia Belt, and to investigate the correlation or not of these rocks with those outcroppings within the dome structures of the northern portion of this belt. This information is important for the organization of the lithostratigraphic framework of the basement of the southern portion of the Araguaia Belt, which in turn is fundamental for understanding the geological evolution of this belt. In the geochronological investigation, the method of evaporation of Pb in zircon single crystals (Pb-Pb in zircon) was used, which provides the crystallization age of zircon obtained from its gradual heating, in a thermal ionization mass spectrometer. A plateau age of the zircon grain is then calculated, on a 207Pb/206Pb versus temperature plot. Granodiorite gneisses with associated leucosomes and calciosilicate gneisses originally correlated to the Colméia Complex (samples SH12, SH15 and SH40), tonalytic gneisses and syenitic gneisses included in the Rio dos Mangues Complex (samples SH36 and SH33) and a sample of Serrote Granite. In the set of rocks that had been correlated to the Colméia Complex, the ages obtained were concentrated around 2.0 Ga, and the zircons of the leucosomes of the calcosilicate gneisses provided a relatively younger age of 1.8 Ga. In the group of rocks mapped as Complexo Rio dos Mangues, the age obtained for the zircons of the syenitic gneisses was relatively younger (1.0 Ga). These gneisses, due to their proximity to the alkaline gneisses of Serra da Estrela and because they are compositionally similar to them, should be part of the Monte Santo Suite. In the analysis of the zircons of the tonalytic gneisses, a plateau age was not defined and, on the contrary, it showed a pattern of continuous growth of the ratio , 207Pb/206Pb, and at higher temperatures, the ages systematically presented values slightly higher than 2.0 Ga . In this case, the oldest ages were assumed as minimum crystallization ages for these zircons. For the Serrote Granite, the age obtained through this method was 1851 ± 41 Ma (2σ). The ages of the gneissic rocks in the basement of the southern segment of the Araguaia Belt, located between 1.8 and 2.1 Ga, indicate the absence of gneisses of Archean ages in this portion of the belt. Consequently, it is advised against correlating them with those of the Colméia Complex. It is additionally suggested to abandon the aforementioned term and extend the name of Complexo Rio dos Mangues to the calciosilicate and orthogneisses that have expression in the vicinity of Paraíso de Tocantins. The crystallization ages of Serrote Granite (1851 ± 41 Ma, 2σ) and Cantão Gneiss (1846 ± 64 Ma) are very similar. Due to this similarity, an additional geochronological study was carried out using the Pb-Pb method in whole rock and feldspars, aiming to investigate the correlation between these granitic rocks. For the Serrote Granite, an age of 1872 ± 140 Ma (1σ) was obtained and for the Cantão Gneiss, an age of 1744 ± 27 Ma (1σ). These ages, when compared with those obtained by the Pb-Pb method in zircon, show that the Pb-Pb system in whole rock was partially opened, during a thermo-tectonic event subsequent to the crystallization of these rocks, rejuvenating their ages. A comparative study was also carried out between these units and some anorogenic granites of Proterozoic age from the Amazon region and the Median Massif of Goiás, where it was verified that the Serrote Granite is very similar to the same ones, also adjusting to the curves of evolution of Pb, proposed in the plumbotectonics model. The Cantão Gneiss does not fit the plumbotectonic model, due to the high 206Pb/204Pb ratios found in the feldspars of the samples from this unit. These high Pb ratios in these rocks reveal that they are enriched in U, and this enrichment may have come from the magma that generated them or have been acquired in a metamorphic event subsequent to its crystallization.
Acesso aberto (Open Access)
Geologia Isotópica U-Pb e Lu-Hf no tonalito Cândido Mendes e arenito da formação igarapé de areia: aplicação em proveniência sedimentar e implicações para evolução do cráton São Luís
(Universidade Federal do Pará, 2023-10-16) FERREIRA, Fernanda Batista; MOURA, Candido Augusto Veloso; http://lattes.cnpq.br/1035254156384979
Using the Lu-Hf isotopic signature in zircon of known U-Pb age allows the characterization of the magma that crystallizes this mineral. Thus, it is a potential tool for sedimentary provenance investigation. The application of this method in provenance studies was tested using detrital zircons from sandstones of the Igarapé de Areia Formation, occurring in the São Luís Cratonic Fragment (SLCF) and the Gurupi Belt (GB) in the Gurupi region, NE of Pará an NW Maranhão. Most zircon grains of the sandstone have Rhyacian age, which allows for evaluating the applicability of the Lu-Hf isotopic system for provenance studies. The morphological analyses of these zircon grains indicate a magmatic origin. The U-Pb data yield Ryancian (2051 to 2256 Ma) and Orosirian (1912 to 2049 Ma) ages. These ages are compatible with the timing of the orogenic event that formed the SLCF. The Bom Jesus Granodiorite, a large granitoid from the Intrusive Tromaí Suite of the SLCF, is representative of the Paleoproterozoic calc-alkaline magmatic event and has a U-Pb zircon concordant age of 2149±5.4 Ma. The Lu-Hf isotopic signatures of the zircons of both tonalite and sandstone are similar, with ƐHf(t) ranging from 0.65 to 6.82 and from 1.84 to 6.07, respectively. Furthermore, the zircon model ages show similar results, with Hf-TDMC from 2.36 to 2.53 Ga for the Igarapé de Areia Formation and from 2.28 to 2.67 Ga for Intrusive Tromaí Suite, indicating a source area for the sandstone made up by juvenile Paleoproterozoic crust. These results support the hypothesis that the sedimentary sources of the sandstone were the rocks located in the SLCF and GB and their Birimian equivalents in the West African Craton (WAC). The lithological and geochronological similarity of the Paleoproterozoic rocks of the Gurupi region with rock units from the Baoulé-Mossi Domain from WAC is well established. In turn, Neoarchean Hf TDMC model ages may indicate a small contribution from the Archean crust, which is recorded more clearly in the rocks of the Baoulé-Mossi Domain. This contamination process may have occurred during the subduction and melting of sediments from the Archean crust or by incorporating a Paleoproterozoic Island arc into Archean terranes. The Lu-Hf isotope system has proved to be a handy tool for investigating sedimentary provenance.
Acesso aberto (Open Access)
Investigação da aplicabilidade da composição isotópica de oxigênio, hidrogênio e estrôncio na autenticação de águas naturais engarrafadas e/ou comercializadas no Estado do Pará – Brasil
(Universidade Federal do Pará, 2020-12-15) BORDALO, Adriana Oliveira; MOURA, Candido Augusto Veloso; http://lattes.cnpq.br/1035254156384979
Bottled water obtained directly from natural sources or by extracting groundwater, in theory, is considered as good quality water, naturally pure, captured in environments free from pollution or contamination, therefore, considered a safe food. However, in addition to the vulnerability to which aquifers may be subject, the final product can be manipulated or even defrauded when considering the increasingly competitive and expanding market in bottled water. Therefore, it is recommended that the manufacturers of this segment look for strategies that highlight, differentiate, or add qualities of bottled water. The guarantee of the origin of its source, determined by analytical methods, can guarantee its quality and add important information to the consumer and their producers. Isotopic analyzes combined with chemical analyzes have been used in research on food products as a tool to identify and authenticate the geographical origin, certify and still control the quality, aiming at the safety of these foods. Also, isotopic analyzes can be used as excellent tracers assisting in forensic science. The isotopic compositions of hydrogen, oxygen, and strontium from bottled waters reflect, on average, the isotopic composition of the spring water, indicating that they preserve information about the water source from which they were bottled. In this context, this work proposed investigating the applicability of the isotopic composition of strontium, oxygen, and hydrogen as a tool to characterize, authenticate, and certify bottled waters. Between 2017 and 2019, several brand bottled waters were sampled in supermarkets of Belém, state of Pará. This sampling was conducted by observing the lithostratigraphic units of the water source, geographical locations, filling dates, and the bottle's validity. The work was carried out in two ways. In the first, seven samples were acquired periodically considering the filling date corresponding to the periods, drought and rainy, completing two seasons cycles. The second sought to assess any chemical and isotopic changes over the course of a year. In this case, samples of four different brands were acquired simultaneously and analyzed quarterly, from the filing date, including a water sample from Italy (sample IT). The waters bottled in Brazil used in this study, in general, have low mineralization (average of 87.2 mg L-1 STD). From a hydrogeochemical point of view, most waters were classified as chlorinated or bicarbonated. The minor and trace constituents contents were significantly lower than the limits recommended by the relevant legislation. The 87Sr/86Sr ratio and strontium concentration permitted to characterize three distinct groups of water. Group 1 is formed by bottled waters in the state of Pará with lower values of δ87Sr (water samples PV = 4.74 ‰, PSI = 10.5 ‰ and PB = 5.87 ‰), and lower concentrations of Sr2 + (2.76 μg L-1). These waters come from the Barreiras Aquifer, which consists of Miocene sedimentary rocks. It is a shallow aquifer with the direct influence of the rainwater. Group 2 is characterized by presenting intermediate values of δ87Sr and higher strontium ion concentrations (average of 110.3 μg L-1). It is formed by bottled waters in the states of Ceará (sample CH = 13.5 ‰), São Paulo (sample SPL = 11.9 ‰) and Paraná (sample PRCL = 18.8 ‰). The first one (CH) comes from the Barreiras aquifer, where the sedimentary rocks of the Barreiras Formation lie on the Paleoproterozoic crystalline basement. The aquifers of the other two water samples are in Proterozoic orthogneisses (SPL) and metasedimentary rocks (PRCL). The third group consists of bottled water in the state of Bahia (sample BA), whose aquifer is in the Lower Cretaceous São Sebastião Formation. This well is the deepest among the studied waters. It presents much higher values of δ87Sr (mean of 43.12 ‰) and intermediate values of Sr2+ concentration (mean of 12.75 μg L-1). The average values of δD and δ18O for these waters were as follows: PV (-15.4 ‰ and -3.26 ‰), PSI (16.6 ‰ and -3.42 ‰), PB (-15.4 ‰ and -3.23 ‰), CH (-13.6 ‰ and -2.95 ‰) BA (-2.07 ‰ and -1.79 ‰), SPL (-41.7‰ and -6.59 ‰) and PRCL (-32.4 ‰ and -5.66 ‰). The values of δD and δ18O were aligned along the global meteoric water line and were more enriched in the heavy isotopes in the north and northeast regions of the country. The range of variation of the isotopic data and the analytical parameters analyzed within the same sample was small, showing no dependence on seasonal influence. The geochemical data obtained were consistent with the information contained on the labels. The study regarding the shelf life of bottled waters (samples PB, SPL, SPCJ, and IT) indicated no significant variations in the chemical and isotopic composition of the elements analyzed over the twelve months period. Considering this information, the isotopic composition of bottled waters must preserve that of their sources. Thus, it was possible to characterize some of the sources individually using the obtained isotopic data. CH (δ87Sr = 13.5‰, δD = -13.6 ‰ and δ18O = -2.95 ‰); BA (δ87Sr = 43.1 ‰, δD = -2.07 ‰ and δ18O = -1.79 ‰); SPL (δ87Sr = 11.9 ‰, δD = -41.7 ‰ and δ18O = -6.59 ‰) and PRCL (δ87Sr = 18.8‰, δD = -32.4 ‰ and δ18O = -5.66 ‰). However, in waters from shallower aquifers located in areas with high rainfall and intense recharge (PV, PSI, and PB water sources), this characterization may become more difficult. Isotopic data guarantee digital printing and ensure its applicability as a tool to authenticate the origin of the product "bottled water" however; they are more suitable for aquifers where these waters have greater and more lasting interaction with the percolating rocks.
Acesso aberto (Open Access)
Investigação do registro histórico da composição isotópica do chumbo e da concentração de metais pesados em testemunhos de sedimentos no Lago Água Preta, região metropolitana de Belém-Pará
(Universidade Federal do Pará, 2001-08-02) CARVALHO, Maria Clarindo; MOURA, Candido Augusto Veloso; http://lattes.cnpq.br/1035254156384979
Lake Água Preta is the main water reservoir, which together with Lake Bolonha, constitute the surface water sources for public supply in the city of Belém. Both reservoirs are dams fed by small drainages and water pumped from the Guamá River. These springs are vulnerable to the release of domestic and industrial effluents due to the disorderly urban occupation in their surroundings and their proximity to the Aurá sanitary landfill. In this work, the historical record of the isotopic composition of lead and the concentration of heavy metals in sediment cores from the Água Preta lake was investigated. Different analytical and spectroanalytical methods such as gravimetry, titrimetry, ion exchange chromatography, atomic absorption spectrometry and mass spectrometry were used to obtain the results. In the chemical separation of lead, specific Sr resin (Sr-Spec) was used in Teflon columns, adapting the methodology of Gale (1996). Through preliminary sampling of bottom sediments along the entire length of the Água Preta lake, the distribution of the isotopic ratios of lead and heavy metals was recognized. The lowest values of the 206Pb/207Pb ratio and the highest levels of heavy metals were identified in the lake ramifications close to the urban occupation zones. In this part of the lake, a 77.5 cm column of sediments, called profile 01, was sampled. The highest values of the 206Pb/207Pb ratio were found near the lake dam, which is constantly influenced by the water pumped from the Guamá River; where profile 02 was witnessed with approximately 110 cm of sediment. The 206Pb/207Pb isotopic ratio values were basically grouped into four segments in profile 01 and in three segments in profile 02. -1.20431 in profile 02, refer to the regional isotopic signature. The 206Pb/207Pb isotopic ratio with values varying between 1.19346-1.19602 in profile 02 correspond to the isotopic signature from the influence of suspended sediments in the water of the Guamá River pumped to the lake and whose 206Pb/207Pb ratio is 1. 19225. The isotopic ratios 206Pb/207Pb varying between 1.16223-1.17621 found only in profile 01, correspond to the anthropogenic contribution. The higher averages of heavy metal concentrations in the upper segment of profile 01 justify the interpretation that the lower values for the 206Pb/207Pb ratio are characteristics of anthropogenic contribution. The average levels of heavy metals, found at the top of profile 02, probably reflect the contribution of suspended sediments from the Guamá River to the Água Preta lake, evidenced by the 206Pb/207Pb ratio. The lower values of the average concentrations of the metals found at the base of two profiles reinforce the interpretation that the higher values of the 206Pb/207Pb ratio reflect a regional contribution, prior to anthropogenic action, basically given by the rocks in the area.
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Proveniência das rochas metassedimentares do cinturão Araguaia, com base em datações em idades modelo Sm-Nd em rocha total e datação Pb-Pb em zircão.
(Universidade Federal do Pará, 2005-06-30) PINHEIRO, Bruno Luís Silva; MOURA, Candido Augusto Veloso; http://lattes.cnpq.br/1035254156384979
The Araguaia belt is an important geotectonic unit of the Tocantins Structural Province, developed during the amalgamation of the West Gondwana Supercontinent during the Neoproterozoic. This belt is located on the border of the Amazon Craton and divides two different crustal segments: to the east there are terrains affected by thermo-tectonic events related to the Gondwana amalgamation. In the west side, terrains not affected by these PanAfrican/Brasiliano events occur. Generally, it has been suggested that the Araguaia belt, was installed in a continental rift basin, developed on Archean crust, without formation of expressive oceanic crust. Afterwards, tectonic inversion took place with mass transportation toward NW forming this belt. However, geochronological studies have shown that the Araguaia belt lies over Archean basement in the north and Paleoproterozoic rocks in the south. In addition, pillow basalts, located in the western region of the Araguaia belt, presented inherited (?) zircon crystals with ages around 2.05 Ga. These data suggest that the contribution of Paleoproterozoic crustal material may have been an important source for the metasedimentary rocks of the Araguaia belt, too. The answer of this question is fundamental for reconstruction of the paleogeographic evolution of the Araguaia belt in the context of the West Gondwana evolution. In this dissertation, single zircon Pb-evaporation ages in quartzites and Sm-Nd model ages in metasedimentary rocks of the Araguaia belt were determined, in order to identify the ages of the possible sources of these rocks and to contribute to understanding the paleogeographic evolution of this belt and West Gondwana. Detritic zircon crystals of two quartzite samples of the Morro do Campo Formation were dated by the single zircon Pb-evaporation technique. The sampling was carried out in the northern segment (Xambioá region), and in the southern segment (Paraíso do Tocantins region) of the Araguaia belt, both in the state of Tocantins. The zircon ages of the quartzite from Xambioá range from 3.0 to 2.65 Ga. On the other hand, a main contribution of Meso-Neoproterozoic terrains (1.25 – 0.85 Ga), with minor of Paleoproterozoic sources (1.75 – 1.85 Ga), is shown by detritic zircons of the southern segment of the belt. These data indicate the contribution of source areas with distinct ages for the metasedimentary rocks of the Araguaia belt. Sm-N model ages (TDM) of the metassedimentary rocks sampled along the Araguaia belt presented a bimodal distribution, with ages showing a major frequency between 1.4 and 2.1 Ga and a minor frequency between 2.4 and 2.7 Ga. These TDM ages suggest that the metasedimentary rocks of the Araguaia belt may result from Paleoproterozoic terrains mixed with younger sources, probably, of Meso- Neoproterozoic ages. Alternatively, this mixing may had a minor contribution from Archean crust. As a result of these isotopic data, it is suggested that the sources of the metassedimentary rocks of the Araguaia belt are located to the east of the belt. The sediments were deposited in oceanic basins along these segments, and were thrust over the eastern margin of the Amazon Craton, due to the amalgamation of the West Gondwana, resulting in the formation of the Araguaia belt. The presence of detritic zircon of Archean age in the quartzite from Xambioá does not necessarily implies in an Archean source located in the Amazon Craton, since Archean rocks are also present in the possible source areas situated to the east of the Araguaia belt. Moreover, these detritic zircon crystals may have been recycled during sedimentary processes and incorporated in rocks units of younger terrains. The main candidates for crustal sources of the metassedimentary rocks of the Araguaia belt are the rock units of the São Francisco Craton, the Goiás Massif and the Goiás Magmatic Arc. These source areas are located to the east of the Araguaia belt and have magmatic rocks with ages similar to those determined in the detritic zircon crystals. In addition, the mixing of rocks from these different terrains may result in the range of the observed TDM ages of the meatssedimentary rocks. The amalgamation of the Paraná Craton, presently under the Paraná sedimentary basin, with the São Francisco Craton, the Goiás Massif and the terrains of the Goiás Magmatic Arc, resulted in the formation of the Brasília belt and in a huge crustal block. The oblique collision of this block with the Amazon Craton, 50 to 100 Ma after the formation of this block, may have led to the SE to NW tectonic transport that thrust different rock units over the eastern margin of this craton, resulting in the formation of the Araguaia belt.
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Proveniência das rochas metassedimentares do setor norte do Cinturão Araguaia com base em geocronologia U-Pb em zircão
(Universidade Federal do Pará, 2022-02-24) MARINHO, Luísa Cardoso; MOURA, Candido Augusto Veloso; http://lattes.cnpq.br/1035254156384979
The Araguaia Belt is an orogen in central Brazil formed during the West Gondwana assemblage by the end of the Neoproterozoic. Phanerozoic rocks of the Parnaíba Basin cover the north and east portion of the belt. The Amazonian Craton limits the Araguaia belt to the west and the Goiano Massif in the south and southeast. The metasedimentary rocks of the belt are assemblage in the Estrondo (quartzites and schists) and Tocantins (schists, phyllites, and metarenites) groups. Detrital zircon from quartzite of the Morro do Campo Formation (lower Estrondo Group), dated by the Pb-evaporation method, revealed populations of different ages for the northern (Xambioá) and southern (Paraíso do Tocantins) regions of this orogen (Pinheiro et al., 2011). Quartzite from Xambioá presented detrital zircon ages between 1.4 and 3.1 Ga, with the main population between 2.6 and 3.0 Ga. In Paraíso do Tocantins the quartzite showed ages varying between 0.7 Ga and 2.8 Ga, but those within 1.0 and 1.2 Ga are predominant. Later, LA-MC-ICP-MS U-Pb zircon dating (Gorayeb et al., 2020) confirmed the expressive contribution of Mesoproterozoic detrital zircon in quartzites from the southern segment of the Araguaia Belt. However, the low sampling density and the analytical limitations of the Pb-evaporation technique do not allow a clear definition of the source area of these sediments. Thus, this work extended the LA-MC-ICP-MS U-Pb dating in detrital zircon for the quartzites of the northern segment of the Araguaia Belt to obtain more accurate ages and define the source area of these sediments. The metasedimentary rocks of the Morro do Campo Formation form several dome-like structures along the northern segment of the belt, in the core of which Archean and Paleoproterozoic basement orthogneisses crop out. The studied quartzites were sampled, from north to south, at the Xambioá, Grota Rica, Cantão, and Colmeia structures. In the Xambioá structure, the quartzite presented the main population with ages between 1600 – 2000 Ma (62%) and three secondary populations of ages 2420 – 2760 Ma (21%), 1430 – 1580 Ma (12%), and 2140 – 2360 (5%). For the quartzite of the Grota Rica structure, the data revealed the main population between 1600 – 1880 Ma (42%) and three secondary populations of ages 2640 – 2990 Ma (25%), 1240 – 1580 Ma (24%), and 1920 – 2080 Ma (9%). The quartzite of the Cantão structure showed the main population with ages between 1300 – 1600 Ma (54%) and three secondary populations with ages of 1600 – 1900 Ma (29%), 1030 – 1300 Ma (11%), and 800 – 950 Ma (5%). Finally, in the Colméia structure, the a main population was defined aged between 980 – 1280 Ma (81%) and two secondary populations aged 2840 – 3000 Ma (10%) and 1850 – 2080 Ma (9%). The ages obtained showed a wide variation of detrital zircon populations. However, quartzites from the structures of Xambioá and Grota Rica register significant contributions of zircon grains from the Paleoproterozoic (Siderian-Riatian-Orosirian-Statherian) and, secondarily, from the Meso-Neoarchean. In the quartzites of the structures of Cantão and Colméia, located further south, Mesoproterozoic detrital zircons predominate (Ectasian/Callimian/Sthenian), and in the latter the presence of zircons stenianos is relatively more expressive. On the other hand, the similarity between the detrital zircon populations from Colmeia and Paraíso do Tocantins indica quartzites that the contribution of rocks formed in the Stenian is not restricted to the southern portion of the Belt Araguaia. Comparison of U-Pb zircon ages of rocks from Massif terrains Goiano/Goiás Magmatic Arc and the Amazon and São Francisco cratons with the detrital zircon ages of quartzites from the Araguaia Belt suggest the terrains of the Goiano Massif/Goiás Magmatic Arc as the most likely source of the sediments. These terrains encompass rocks with ages corresponding to zircon populations. found, and constitute the crustal segment closest to the basin precursor of the Araguaia orogen. Furthermore, they occupy a geographical position compatible with a source area situated to the southeast of this belt, as suggested by previous works of sedimentary origin. It is also recommended to complement the provenance study of quartzites using the Lu-Hf method in zircon for better characterize source areas based on ƐHf values and Hf-TDM model ages C.
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Proveniência dos arenitos dos grupos Canindé, bacia cratônica do Parnaíba, por termocronologia e geocronologia em zircão detrítico.
(Universidade Federal do Pará, 2023-11-27) OLIVEIRA, Camila Vilar de; MOURA, Candido Augusto Veloso; http://lattes.cnpq.br/1035254156384979
Before the most severe Late Paleozoic Ice Age, the Western Gondwana was affected by short-lived glaciations recorded in several intracratonic basins from Northern South Amer ica. The Famenian-Tournasian coastal marine successions exposed in the Sulamerican plat form represent a window of opportunity to unravel the different source lands using U-Pb ages of detrital zircon grains during the icehouse and greenhouse conditions. The Famenian Tournasian Cabeças Formation in the intraplate Parnaiba basin, Northern Brazil, represents a glaciomarine system of the ice contact delta developed at the Western Gondwana Margin. Preglacial deltaic deposits indicate two significant U-Pb age peak ranges of 768-448 Ma and 1175-937 Ma, suggesting drainage from the East of Western Gondwana. In contrast, U-Pb age peak ranges of 1998-1731 Ma and 1079-894 Ma show sources from the South supplying the northwestern glacier advance on the coastal-marine settings. During the initial greenhouse phase, the ice-melt deltaic system provided zircon ages of 1093-817 Ma, indicating the retak ing of the preglacial source lands. The sampling for age acquisition combined with precise paleoenvironmental interpretation offers, for the first time, high-resolution information that supports a most robust paleogeographic reconstruction of the Western Gondwana during the Late Paleozoic. Additionally, the use of Hf isotope and fission track proxies linked to a sys tematic morphological description, internal structure, and Th/U ratio applied to Mesoprotero zoic-Tonian detrital zircons, focused on the main detrital age spectra of glacial deposits, al lowed reveals the discrimination of competing sedimentary source land regions and recogniz ing detrital contributions from the provenance dynamic of ancient orogenic settings, such as the West Gondwana and Araçuai-West Congo orogens.
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Termocronologia por traços de fissão em apatita da Borba Sul da Bacia do Amazonas, na região de Itaituba (PA)
(Universidade Federal do Pará, 2010-11-09) PINA, Aline Carla Miranda de; LELARGE, Maria Lidia Vignol; http://lattes.cnpq.br/3165548495925769; MOURA, Candido Augusto Veloso; http://lattes.cnpq.br/1035254156384979
The region of Itaituba (PA) located at the South portion of the sedimentary basin of the Amazon can be defined as a border zone between this basin and the Amazonian Craton. In this region outcrop sedimentary rocks, belonging to Pitinga, Maecuru, Ererê, Barreirinha, Curiri, Monte Alegre and Itaituba Formations, representatives of sineclise phase sedimentary basin of the Amazon; sedimentary rocks the stage rift gathered in Prosperança Formation; besides igneous rocks of Iriri Group, Parauari Intrusive Suite and Maloquinha Intrusive Suite, which compose the basement of the sedimentary basin. The fission track thermochronology of apatite was used in the investigation of thermotectonic evolution of the sedimentary basin of the Amazon region of Itaituba (PA), mainly from the dating of basement rocks of the basin. The method of fission tracks in apatite is a marker thermochronologic low temperature, recording temperatures of up to 120 º C. When subjected to conditions of temperatures above the traces of apatite fission are cleared, resetting the clock geochronological for this method, and registers, thus, a new event. Thus, this tool was used to investigate the age of the tectonic processes that affected the Amazon Basin, which were also recorded in the rocks of its basement. Given the scarcity of apatite in sedimentary rocks sampled units of the Amazon basin, only a sample of the Monte Alegre Formation sandstone has been dated by fission track method. However, in the basement could be dated 20 samples, representing various rocks including rhyolites, granites and olivine-diabase of Paleoproterozoic, belonging to the three units mentioned above. The sandstone of the Monte Alegre Formation, whose age of the lithostratigraphy and Mesocarbonífero, provided apparent ages in apatite fission track AFT) from 91 Ma. Statistically this sample revealed the existence of two populations of apatite grains: a population with a mean age of 105 Ma and another population with a mean age of 64 Ma, indicating that this sample was subjected to two events thermotectonic. This fact can be confirmed through the thermal modeling also showed that the presence of two events whose ages are 106 Ma and 58 Ma. Samples of the basement were divided into three groups according to ages TFA obtained and the results of mathematical models. In group 1 TFA ages ranged from 163.0 Ma and 258.7 Ma, for group 2 ages were established between 142.1 Ma and 147.4 Ma, while samples of group 3 were between 170.1 Ma and 180.9 Ma is noteworthy that the ages of crystallization of igneous bodies sampled are between 1.8 and 1.9 Ga. The mathematical modeling of samples of groups 1 and 2 record the same epsódios, a first cooling, followed by heating and finally an episode of cooling. This last cooling event occurred about 100 Ma for all samples of these groups, except the sample IT-16 passing through the final event of cooling for 62 Ma. The thermal histories of samples IT-22 and 23 show a period of accelerated cooling compared to previous samples, their thermal histories ending at 39 Ma and 35 Ma, respectively, suggesting the existence of neotectonic events in the region. The events of approximately 100 Ma recorded in the Monte Alegre Formation sandstone and models of the samples of the basement can be related to a compressional tectonics that occurred according to the opening of the eastern equatorial Atlantic and the convergent movement of Andean subduction zone, west of South American plate. In turn the events of Tertiary age (64-58 Ma) marked these rocks may show reflections of a process where dextral transform interacted plates South American, Caribean and Nazca, reactivating old fracture zones. The various ages obtained for samples of the basement (ranging from 142.1 Ma and 258.60 Ma) are markers of major tectonic events, but may be registering the different ages at which these samples passed by the isotherm of 120 ° C, indicating thus the occurrence of a tectonic with different behavior in different areas of this region.